Bulk up, baby

"Why did you decide to be a personal trainer?" Izumi asked, her face turned too stare into Katsumi's eyes. She watched as Katsumi stumbled to find the words.

"Well. When I was younger, I was fat." She chose terms that were direct and forthright. "Started going to the gym at around 13, and then decided that I loved it so much I wanted to show others how much joy it can bring. Some of my clients bail on the first day, and that's their loss, because the gym provided me with solace for years. They just can't handle all this." Katsumi gestured to her physique, smiling as Izumi chuckled in response.

"They just couldn't handle the burn. But you can, right?"

"Of course I can."

**
Or: fem!bkdk, but Izuku is chubby and wants to change, and Katsuki ends up being her gym trainer